springboot-tdd

Use @ExtendWith(MockitoExtension.class) with @Mock for dependencies and @InjectMocks for the service under test. Stub with when(...).thenReturn(...) and verify interactions with verify(repo).save(any()), following the Arrange-Act-Assert pattern.

Use @WebMvcTest(YourController.class) with an autowired MockMvc and @MockBean for the service layer. Perform requests with mockMvc.perform(get("/api/...")) and assert responses using status().isOk() and jsonPath expressions.

@WebMvcTest loads only the web layer with mocked services, making it fast for controller tests. @SpringBootTest boots the full application context for end-to-end integration tests, typically combined with @AutoConfigureMockMvc and a test profile.

Combine @DataJpaTest with @AutoConfigureTestDatabase(replace = Replace.NONE) and import a Testcontainers configuration class. Use @DynamicPropertySource to inject the container's JDBC URL into the Spring context so tests run against a real Postgres or Redis instance.

Add the jacoco-maven-plugin with the prepare-agent goal and a report execution bound to the verify phase. Run mvn verify or ./gradlew test jacocoTestReport to generate coverage reports and check them against your 80% target.